Unique biogenesis and kinetics of hornwort Rubiscos revealed by synthetic biology systems  

作　　者：Zhen Guo Oh Tanner Ashton Robison Dan Hong Loh Warren Shou Leong Ang Jediael Zheng Ying Ng Fay-Wei Li Laura Helen Gunn 

机构地区：[1]School of Integrative Plant Science,Cornell University,Ithaca,NY 14853,USA [2]Boyce Thompson Institute,Ithaca,NY 14853,USA [3]Max Planck Institute for Terrestrial Microbiology,35043 Marburg,Germany [4]Department of Cell and Molecular Biology,Uppsala University,75124 Uppsala,Sweden

出　　处：《Molecular Plant》2024年第12期1833-1849,共17页分子植物（英文版）

基　　金：National Science Foundation grant no.MCB-2213840 to L.H.G.and MCB-2213841 to F.-W.L.

摘　　要：Hornworts are the only land plants that employ a pyrenoid to optimize Rubisco’s CO_(2) fixation,yet hornwort Rubisco remains poorly characterized.Here we assembled the hornwort Anthoceros agrestis Rubisco(AaRubisco)using the Arabidopsis thaliana SynBio expression system and observed the formation of stalled intermediates,prompting us to develop a new SynBio system with A.agrestis cognate chaperones.We successfully assembled AaRubisco and Rubisco from three other hornwort species.Unlike A.thaliana Rubisco,AaRubisco assembly is not dependent on RbcX or Raf2.Kinetic characterization reveals that hornwort Rubiscos exhibit a range of catalytic rates(3–10 s−1),but with similar affinity(∼30μM)and specificity(∼70)for CO_(2).These results suggest that hornwort Rubiscos do not comply with the long-held canonical catalytic trade-off observed in other land plants,providing experimental support that Rubisco kinetics may be phylogenetically constrained.Unexpectedly,we observed a 50%increase in AaRubisco catalytic rates when RbcX was removed from our SynBio system,without any reduction in specificity.Structural biology,biochemistry,and proteomic analysis suggest that subtle differences in Rubisco large-subunit interactions,when RbcX is absent during biogenesis,increases the accessibility of active sites and catalytic turnover rate.Collectively,this study uncovered a previously unknown Rubisco kinetic parameter space and provides a SynBio chassis to expand the survey of other Rubisco kinetics.Our discoveries will contribute to developing new approaches for engineering Rubisco with superior kinetics.

关 键 词：HORNWORTS CO_(2) fixation RUBISCO synthetic biology structural biology assembly factors 

分 类 号：Q94[生物学—植物学]